Transitions are times of danger in virtually all areas of human life. More accidents are likely to occur when cars go in and out of parking spaces, or when planes take off or land. More medical mishaps are likely to happen in hospitals when there is a change in shifts between nurses. The same pattern holds in the law of pharmaceutical patents, during the transition from a fully proprietary regime to one that allows for as many firms as possible to market a generic version of a once-protected pharmaceutical patent.To pass judgment on these issues, it is often necessary to ask the thankless question of whether the supposed advances in science exceed the preclusive effect that arises if the original product is removed from the Orange Book—or official FDA registry of drugs available for sale—in ways that limit competition.